The above consideration indicates that at present many of the experi mental facts on PS in animals can be quantitatively explained within the limits of the "universal" photoreceptor membrane concept. Of course, existence of preferential orientation of the absorbing dipoles in the tubuli of the rhabdomeres can not be totally rejected. We hope that the concept of the "universal" photoreceptor membrane may serve as the useful instrument when dealing with newly discovered properties of visual cells so that true mechanisms of electrical and optical coupling will be searched for instead of assumptions being made on additional properties of the photoreceptor membrane in every new animal under study. 5. Absorption Spectrum of the Universal Photoreceptor Membrane and Spectral Sensitivity of the Photoreceptor 5. 1 Preliminary Notes It seems nearly self-evident that the absorption spectrum of the pho toreceptor membrane coincides exactly with that of the visual pigment it contains. Hence, the membrane must exhibit three bands of absorp tion - the principal band with its peak within the limits of visible spectrum (or a-peak); the secondary band between 340 and 380 nm (S peak); and the third, protein band, in the ultraviolet (UV) at 280 nm (COLLINS et al., 1952). The main peak of absorption is located within the range 433-575 nm for retinol-based pigments and between 438 and 620 nm for 3-dehydroretinol-based pigments, the position of Amax de pending on many ecological factors."

In the comparative physiology of photoreception by the Protista and the invertebrates two aspects are emphasized: (1) the diversity of visual processes in these groups and (2) their bearing upon general mechanisms of photoreception. Invertebrates have evolved a far greater variety of adaptations than vertebrates modifications aiding survival in the remarkably different biotopes they occupy. The number of species in itself suggests this multiformity; each of them has peculiarities of its own, in morphology as well as in physiology and behavior. But these special adaptations are variations on a few great themes. Although the catalogue of invertebrate species is immense, the literature concerning them nearly rivals it in extent-even if one considers only that fraction dealing with visual physiology. Taxonomy proceeds by grouping the species, categorizing them in genera, families, orders, and progressively larger units. Similarly, comparative physiology aims at an analogous, more or less compre hensive, classification. This Part A of Volume VII/6, like Part B that follows it, emphasizes the broad questions that concern groups larger than the individual species; in some cases these questions have general applicability. The middle course between approaches that are too specialized and those that are too general is often elusive, but here we attempt to follow it. The vast number of special adaptations-probably, as we have said, as large as the number of species-is beyond the range even of a handbook."

This text is intended to provide an in-depth, self-contained, treatment of optical waveguide theory. We have attempted to emphasize the underlying physical processes, stressing conceptual aspects, and have developed the mathematical analysis to parallel the physical intuition. We also provide comprehensive supplementary sections both to augment any deficiencies in mathematical background and to provide a self-consistent and rigorous mathematical approach. To assist in. understanding, each chapter con centrates principally on a single idea and is therefore comparatively short. Furthermore, over 150 problems with complete solutions are given to demonstrate applications of the theory. Accordingly, through simplicity of approach and numerous examples, this book is accessible to undergraduates. Many fundamental topics are presented here for the first time, but, more importantly, the material is brought together to give a unified treatment of basic ideas using the simplest approach possible. To achieve such a goal required a maturation of the subject, and thus the text was intentionally developed over a protracted period of the last 10 years."

This text is intended to provide an in-depth, self-contained, treatment of optical waveguide theory. We have attempted to emphasize the underlying physical processes, stressing conceptual aspects, and have developed the mathematical analysis to parallel the physical intuition. We also provide comprehensive supplementary sections both to augment any deficiencies in mathematical background and to provide a self-consistent and rigorous mathematical approach. To assist in. understanding, each chapter con centrates principally on a single idea and is therefore comparatively short. Furthermore, over 150 problems with complete solutions are given to demonstrate applications of the theory. Accordingly, through simplicity of approach and numerous examples, this book is accessible to undergraduates. Many fundamental topics are presented here for the first time, but, more importantly, the material is brought together to give a unified treatment of basic ideas using the simplest approach possible. To achieve such a goal required a maturation of the subject, and thus the text was intentionally developed over a protracted period of the last 10 years."

Over the past decade or more, the art relating to modern optical waveguides has evolved as a nighly focused interdis ciplinary field, so attractive, stimulating and full of far reachin3 promise that no parallel could be found earlier in other branches of applied sciences except, perhaps, in solid state electronics and computer technology. This Proceedings, with a selection of 53 papers and briefs by 96 authors of 16 countries, is of real internation al dimensions. It is the outgrowth of the International Symposium held June 20-23, 1983, the first international meeting on this subject taking place in China. Since almost every country in the world, Eastern or ~;estern, large or small, has been involved in the study and promotion of this technological revolution, it is only natural that China snoula be happy to serve as host country of the international meeting to promote an interchange of experiences and iaeas conducive to greater achievements in the future.